1. Field of the Invention
This invention is concerned with an improved method of preparing alkaline earth metal carbonate-overbased alkaline earth metal sulfonates which are useful as detergent and reserve alkalinity lubricating oil additives. More specifically, the object of the present overbasing technique is to obtain a complex or micellar dispersion of calcium carbonate in the presence of a surfactant type material such as a neutral calcium sulfonate.
2. Prior Art
In connection with this invention, the applicant is aware of U.S. Pat. Nos. 3,524,814; 3,878,116 and 4,086,170.
The prior art for overbasing calcium sulfonates employs either calcium hydroxide or calcium oxide but not a combination of the two as the inorganic calcium source. When calcium hydroxide is used as the sole inorganic source, a large volume of solids remain after the overbasing is complete and these solids must be removed by filtration or centrifugation. A reduction in the solids content of the crude product improves process economics and reduces solid waste disposal problems. The processes employing calcium oxide as the sole inorganic calcium source require the use of an additional ingredient; a promoter, such as an amine or ammonia (U.S. Pat. No. 4,086,170) or overbasing in stages with solvent removal, water treatment and dehydration steps after each stage (U.S. Pat. No. 3,878,116).